Reduced bone density, which often evolves into osteoporosis in aging populations, especially pre- and post-menopausal women, is an important health concern. Osteoporosis is defined clinically through the measurement of bone mineral density (BMD), which remains the best predictor of primary osteoporotic fractures (Kanis et al., Osteoporos. Int. 16:581, 2005). Systemic inflammation is frequently associated with accelerated bone reabsorption, which leads to bone loss. Various mechanisms, such as elevated PGE2, TNF-α, IL-1β and other pro-inflammatory cytokines, have been proposed to be involved with bone loss under inflammatory conditions (Hardy and Cooper, J. Endocrinol. 201:309, 2009).
It has been shown that NSAIDs inhibit the COX enzyme and decrease production of prostaglandins, which are involved in the regulation of bone turnover (Raisz et al., Osteoporos. Int. 3(Suppl 1):136, 1993). The use of cyclooxygenase-2 (COX-2) inhibitors has been demonstrated not only to impair load-induced bone formation, but also to prevent menopause-associated BMD loss (Richards et al., Osteoporos. Int. 17:1410, 2006). For example, diclofenac is an NSAID that inhibits both COX-1 and COX-2 enzymes (Richards et al., 2006). In a human clinical trial, diclofenac was almost as effective as conjugated estrogens for protection of bone loss in postmenopausal women (Bruce et al., Am. J. Med. 96:349, 1994). Cottrell et al. (Bone Joint Res. 2:41, 2013), have reported that a 5-lipoxygenase (LOX) inhibitor can enhance bone regeneration in an animal model. In human clinical trials in postmenopausal women, regular use of the combination of a COX-2 selective NSAID and aspirin has been shown to result in higher BMD at all skeletal sites, including whole body and total hip, as measured by bone density scanning (DXA) and both trabecular and cortical BMD of the lumbar spine by quantitative computer tomography (QCT) (Carbone et al., J. Bone Miner. Res. 18:1795, 2003).
Osteoarthritis (OA), characterized by progressive degeneration of articular cartilage, osteophyte formation, and subsequent joint space narrowing, is the most common form of arthritis that affects an estimated 30.8 million adult population in the US (Cisternas et al., 2016). Despite recent advances in drug discovery, present-day OA management is inadequate due to the lack of primary therapies proven to be effective in modifying disease progression. The current approach focuses mainly on curtailing the sensitivity of disease associated pain (like use of over the counter Non-steroidal anti-inflammatory drugs, NSAIDs), which will only mask the actual etiology leading to irreversible damage to the articular structure. In addition, chronic usages of NSAIDs for symptomatic relief of OA are also limited due to their gastrointestinal, renal and cardiovascular side effects (Bozimowski et al., 2015). As a result, there always is the need for a safe and efficacious natural alternative.
OA is a multifactorial disease with unspecified initial etiology involving articular cartilage, subchondral bone and synovial membrane. Cartilage is the main component of articular structure, and consists of chondrocytes that are embedded in a dense and highly organized extracellular matrix (ECM). ECM is synthesized by the chondrocytes, and is composed of a collagenous network that primarily contains type II collagen, along with glycosaminoglycans (GAGs) and associated proteoglycans. Pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1 are known to play important roles in cartilage matrix degradation in the articular cartilage through a cascade of events that lead to stimulation of aggrecanase and matrix metalloproteinase production (Kobayashi et al., 2005). Articular cartilage degradation could also occur as a result of an imbalance in the homeostasis of these fundamental matrix components such as GAGs and type II collagen (Bijlsma et al., 2011). This pathogenesis is triggered in part by the action of inflammatory cytokines, primarily IL-1 (Kapoor et al., 2011; Sandell et al., 2008) that also mediate the production of proinflammatory mediators (including NO and PGE2) and matrix degrading enzymes—aggrecanase and matrix metalloproteinase (MMP). While the catabolic enzymes, MMPs disrupt collagen fibers (Hollander et al., 1994), members of a disintegrin and metalloprotease with thrombospondin (ADAMTS) family degrade aggrecan and both cases result in the release of GAGs (Bondeson et al., 2008). Therefore, plant extracts with proven anti-inflammatory and/or anti-protease/aggrecanase activity could potentially be co-administered with other materials for their potential cartilage protection activity in OA patients.
It is believed that at various stages of OA, all three major structures of the joint (cartilage, subchondral bone and synovium) could be involved in the pathophysiology of the disease which complicates the identification of a single biomarker that is crucial for immediate therapeutic intervention at the early stage of the disease. Nevertheless, among all the major joint biomarkers proposed, C-terminal telopeptide of type II collagen (CTX-II) has been by far the most studied and frequently referred biomarker of cartilage degradation that could be used for the purpose of diagnosis, determining severity of disease or extent of disease progression, prognosis and monitoring efficacy of treatment. It is primarily generated by matrix metalloproteinase activity during cartilage degradation in OA. It is known to show a close link with progression of articular cartilage degradation in OA patients. It's correlation of increased serum, urine or synovial fluid level and articular cartilage degradation were reported both in pre-clinical and clinical studies (Oestergaard et al., 2006; Garnero et al., 2001). However, there is very limited reports suggesting that plant extracts with inherent characteristic of reducing CTX-II level to be also potentially administered for their cartilage protection activity.
One of the challenges for measurement of clinical efficacy of active agent for prevention and treatment of arthritis and for protection of joint and cartilage integrate heavily relies on subjective WOMAC questionnaires for symptom relieve and x-ray and other diagnostic instrument to measure joint space area and joint space narrowing, which requires significant number of subjects and many months long treatment. It is clinically relevant for finding novel natural compositions that can demonstrate modulation of objective clinical measurements such as CTX-II biomarkers associated with joint health.
Recently, we reported a botanical composition designated as UP1306 (a proprietary blend of two bioflavonoid standardized extracts from the heartwood of Acacia catechu and root bark of Morus alba) with analgesic and anti-inflammatory effects which was discovered through the in vivo screening of known traditional folk-medicines suggesting its usage for OA associated symptoms relief (Yimam, et al., 2016). UP1306, administered orally at a dose of 300 mg/kg, resulted in 46.3%-53.3% reductions in paw edema and 43.6%-54.8% reductions in pain sensitivity in the carrageenan induced rat paw edema model as well as a 34.4% reduction in visceral pain sensitivity in the Writhing's model in mice (Yimam et al., 2016). In vitro, it showed dose-dependent inhibition of the enzymatic activities of COX and LOX with IC50 values of 20.9 μg/mL, 49.2 μg/mL, and 11.1 μg/mL in COX-1, COX-2, and 5-LOX, respectively (Yimam et al., 2016).
Previously we have also documented that, a bioflavonoid composition—UP446, which comprises baicalin from Scutellaria baicalensis and catechin from Acacia catechu to possess bioactivities including: (i) dual inhibition of COX and LOX (Burnett et al., 2007) (ii) normalization of COX-2, TNF-α, IL-1β, IL-6, and NF-κB gene expression in lipopolysaccharide (LPS)-induced human and animal cell lines (Tseng-Crank et al., 2010) (iii) inhibition of COX-2, 5-LOX, and inducible-nitric oxide synthase (iNOS) gene expression and moderation of NF-κB binding activity in endotoxin-stimulated rat peritoneal macrophages (Altavilla et al., 20090). Beneficial applications in OA related symptomatic pain relief has also been reported for UP446 from human clinical trials (Sampalis and Brownell, 2012; Arjmandi et al., 2014).
There is no report of using these compositions alone or in combination to reduce CTX-II biomarkers associated with joint health, bone health, or a combination thereof.